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Hands On, Hands Off

Winter House Plant Care Is Awash In Contradiction

January 20, 1995|By Dennis Rodkin. Special to the Tribune.

Wondering how to care for indoor plants during the cold, short days of winter? Here are two important pieces of advice: (1) Give them less attention than they get at any other time of year; and (2) give them more attention than they get at any other time of year.

It's no joke. Although most house plants need nearly constant water and fertilizer during the warm seasons, they prefer to go on a starvation diet while dormant in winter. But at the same time, the indoor climate in winter provides optimum conditions for several varieties of pests, which can devastate plants if left unchecked. So, while food and water should be kept to a bare minimum, house plants still require regular monitoring during winter.

The contradiction isn't lost on Ron Wolford, urban gardening educator at the University of Illinois Cooperative Extension Service. "People who know that house plants go dormant in winter know to stay away from watering," he says, "but that makes them much less attentive to the plants, so they're less likely to discover bugs early on, when it's easiest to control the problem."

Even though they may spend their lives indoors insulated against the change of seasons, house plants are not immune to winter. Short days mean less light to fire plants' major form of sustenance-photosynthesis. In response, they either go into a slow-growth mode or shut down entirely. Continuing to water them at the rate you did when they were growing vigorously is pointless; they have little use for water when half asleep.

Benign neglect

"Everybody has to get used to the idea that house plants like to be neglected in winter," says Janet Cohen, whose Northfield company, Plantscapes, designs and maintains indoor plant arrangements for businesses and residences. "It's hard to get used to, especially because if you keep them indoors you don't think of them as being on an outdoor cycle. But it really doesn't do them any good to keep pouring on the water and fertilizing them all winter."

Cohen says house plant fertilizer should be cut off completely from at least October through March. It's a stimulant, something plants have no use for when they are trying to nap through the dim days of winter. Don't stop watering completely, though. Wolford says to water only when the surface of the soil gets dry-which may happen every two weeks or once a month, depending on the plant and the mixture of warmth and light that surround it. Plants near heater vents will dry out faster than others, and so will plants that sit in front of drafty windows, says Verle Lessig, who co-owns the Fertile Delta garden center on Chicago's North Side.

Each plant will set its own schedule for winter watering. Plant owners who can't quite figure out what a plant wants can always tell when they've given more water than the plant wants, but only if they trust the experts and not their instincts.

As Wolford explains, "Wilting leaves are a symptom of root rot, which is caused by over-watering, but a lot of people will see wilting leaves and think the plant needs more water. That's the last thing it needs." Another symptom of root rot is yellow leaves. Lessig says house plant owners tend to think their charges live by a too-simple equation; if a house plant looks bad, they reason, it needs water. "But it's typical for plants to lose a few leaves and not look their absolute best at that time of year," he says. "Most indoor plants are from the tropics. This is not their favorite place to spend the winter."

Clearly, the consensus among indoor-plant experts is that plant lovers should spend winter fighting the urge to water. But for some people, vigorous leafy house plants provide the only symbol of hope that winter will certainly end and the glorious outdoor seasons will return. For them, time spent examining their house plants for signs of marauding bugs may be a good, if temporary, substitute for time spent in the garden. The plants will be grateful.

Rest is dangerous

"Any plants in a resting stage are more susceptible to disease and pests, but house plants in the winter have another strike against them-all that heat blowing on them from our heaters," Cohen says. In their original, tropical settings, most common indoor plants were accustomed to humid settings, but Cohen says the average relative humidity in a Chicago house in winter is a brittle, skin-drying 4 percent. Already weakened by dormancy, house plants are pushed further into the risk zone by dry indoor weather. That's when plants that seemed healthy and hearty all summer can seem to come down with bad cases of scale insects, spider mites or whiteflies almost overnight. The three tiny bug varieties are the most common house plant pests, and all multiply fast.